Switchable planetary transmissions are intended to provide adequate speed to accessory assemblies, such as an air conditioner compressor, alternator, steering pump or any other kind of auxiliary at engine idling speeds without causing those assemblies to race out of specification at high engine speeds, which may cause damage. This makes it possible to guarantee the operation of the vehicle electrical system, steering system or AC system even if the accessory assembly size might be reduced. Reduced accessory speed at high engine revs leads to lower power losses giving higher maximum performance.
Representative of the art is U.S. Pat. No. 4,827,799 which discloses an infinitely variable planetary transmission is used in a vehicle, such as motorcycle and remote-control model car. The transmission includes a driven shaft journalled within the end bore of an input shaft. A sun gear is sleeved rigidly on the driven shaft. A planet gear carrier is sleeved rotatably on the driven shaft and serves as a power output member. A first centrifugal clutch is interposed between a ring gear and the input shaft so that, when the rotational speed of the input shaft is increased, the ring gear rotates synchronously with the input shaft. A set of planet gears are mounted rotatably on the carrier and meshed with the ring and sun gears. A second centrifugal clutch includes friction shoes mounted on the carrier, and a rim clutch sleeved rigidly on the driven shaft. A uni-directional bearing limits the driven shaft to rotate only in the same direction as the input shaft. When the input shaft rotates at a low speed, the sun gear is fixed by the limiting action of the unidirectional bearing so that the rotational speed ratio of the carrier to the input shaft is low. When the input shaft rotates at a high speed, the second centrifugal clutch interengages the carrier and the driven shaft so that the ring and sun gears rotate in the same direction, achieving a high rotational speed ratio of the carrier to the input shaft.
What is needed is a planetary transmission having a centrifugal clutch and a one-way clutch for selectively directly coupling an input member and an output member. The present invention meets this need.